The present invention relates to an installation system for securing workpieces of composite materials and the like and to a threaded fastener therefor, including a pin and a nut for use in interference applications in such a system.
Many structures are fastened together with swage type fasteners of a lock bolt type, including a pin and a collar, such as shown in U.S. Pat. Nos. 2,531,048 issued to L. C. Huck, on Nov. 21, 1950 for "Fastening Device", RE. 30,445 issued to John H. Ruhl on Dec. 16, 1980 for "Fastener With Proportioned Strength Lock Grooves", and U.S. Pat. No. 4,472,096 issued to John Ruhl and Richard D. Dixon on Sept. 18, 1984 for "Optimized Fastener Construction System and Method". Often these fasteners are installed with a preselected desired interference with the openings in the workpieces. Frequently when such structures are repaired, some of the existing fasteners are removed. The process of removing the fasteners and in preparing the fastener openings in the repaired structure results in the openings being made slightly oversized in contrast to their original size. In fastening the repaired structure, in some instances, it is desirable to use fasteners with pins of the same diameter as those originally used. At the same time, it is desirable that the repair fastener provide the desired interference with the workpiece opening. However, in order to compensate for the larger opening, the pin of the repair fastener can be used with a thin gauged sleeve whereby the difference in diameter between the pin and enlarged opening can be accommodated while providing the desired interference.
It should be understood, however, that the present invention is not limited to repair applications.
In the present invention a fastener assembly including a threaded pin and thin gauge sleeve is used with a threaded nut member. The sleeve is dimensioned to be received with a slight clearance in the workpiece openings and is expanded to the desired interference by the pin as the pin is moved axially through the sleeve to its installed position.
In one form of the invention the axial movement of the pin is effected through a threaded connection by a nut member with the pin. As can be seen from the drawings and the description of the various embodiments, the pin of necessity will have an excess length of threaded shank after installation. In order to eliminate the excess shank length and the resulting excess weight and protrusion, the threaded shank is provided with a breakneck groove or weakened portion at which the excess pin shank portion can be severed with a relatively low bending force or axial load.
In another form of the invention, the axial movement is effected by a pull type tool which exerts the required axial force between the pin and the sleeve to cause the relative axial movement and resultant sleeve expansion.
In any of the various forms of the present invention, the final joint can be secured by a nut member threaded onto the pin shank.
The fastener and method of installation are especially desirable for use with workpieces constructed of crushable materials such as composites or the like. In addition the fastener and method of installation are also desirable in applications where clearance is limited, precluding the use of conventional installation tools.
Therefore it is an object of the present invention to provide a multipieced fastener for securing workpieces via openings therein and a method of installation of such fastener for creating a preselected interference with such workpiece openings.
It is another object of the present invention to provide a fastener for securing workpieces via openings therein with the fastener including a pin, a sleeve and a nut with the pin having a frangible shank portion which can be readily broken away after installation, and a method of installation of such fastener for creating a preselected interference with the workpiece openings.
It is still another object of the present invention to provide a fastener for securing workpieces via openings therein with the fastener including a threaded pin, a sleeve and a threaded nut with the pin adapted to be pulled into the sleeve to create a desired interference with the workpiece openings and a method of installation of such fastener for providing the preselected interference with the workpiece openings.
It is another object of the present invention to provide a multipieced fastener for securing workpieces via openings therein where such workpieces are constructed of crushable materials such as composites or the like, and a method of installation of such fastener for creating a preselected interference with the openings in such workpieces.
It is another object to provide a fastener for securing workpieces via openings therein and method of installation for creating a preselected interference with such openings in workpieces where the clearance around such openings is limited.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.